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| I've been trying to figure out a solid solution for leaky Mopar exhaust flanges, even Remflex gaskets blew out the side after a short while on my 383. My flanges are slightly warped or bowed like they always are, so my next plan is to cut new flanges out of thicker steel, like 1/2" or 5/8" thick plate...I've filed my exhaust manifolds flat, I'm hoping with new Remflex gaskets and thicker, flat flanges, it will be a permanent fix...anyone care to share their experience with this issue? |
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Expert 5K+
Posts: 6513
 
Location: Newark, Texas (Fort Worth) | I have some copper gaskets on a difficult to seal engine. They worked great!
https://www.holley.com/products/gaskets/exhaust_gaskets/parts/7167MR... |
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Expert 5K+
Posts: 8948
Location: WHEELING,WV.>>>HOME OF WWVA | didn't some not use a gasket . what year is the 383 . i know for sure 64 383 didn't use them -----------------------------------------------------later |
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Veteran
Posts: 131
| My solution (as suggested by a pro stock engine builder) is Permatex Ultra Copper and no gaskets. Apply it liberally, bolt it up and wipe off the excess. I've been doing this on the last few engines I put together and it works perfectly. It's high temp, fills the voids and irregularities and doesn't blow out.
http://www.amazon.com/Permatex-81878-Maximum-Temperature-Silicone/d... |
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| Mstrug and Chuck, thanks but I'm talking about the manifold-to-exhaust pipe seal. 5wndwcpe, I tried ultra copper, it lasted about 15 minutes and then disintegrated, couldn't take the heat at all. Although oddly enough it works so far (several months) on my Ford 223 inline six- go figure.
One thing I'm contemplating, besides thicker flanges, is adding the flexible stainless mesh pieces that a lot of newer cars use, somewhere downstream of the flange...might take the stress off the flange with the constant rocking of the engine...? |
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Expert 5K+
Posts: 8948
Location: WHEELING,WV.>>>HOME OF WWVA | well hell , it's a flange gasket ,,,,,,,,,, steel , like oem-----------------------------------------------------later
http://www.ebay.com/itm/Pair-Exhaust-Pipe-Flange-Gasket-W-8-Cyl-Fit...
i've also used vibrant , especially if i think the mating surfaces aren't perfect
http://www.ebay.com/itm/Vibrant-1456-2-Bolt-High-Temperature-Exhaus...
Edited by 60 dart 2016-01-27 12:16 AM
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| Those steel ones would likely work Chuck, though a person would still need to have flat, unwarped surfaces I'd think. And I know from experience the other perforated type ones like Vibrant will absolutely fail unless the flanges are very close to flat. My flanges, when mated together, have a good 1/16" space on either side. Beating the bolt ends back down might help but they will just bend again I'd say when you torque the bolts down.
I'll cut and weld on new flanges on the pipes and report back with my results. The old flanges are only 1/4" thick, not enough clearly, they bend at the bolt ends.
Likely a case where the penny pinchers at Chrysler were to blame!
Edited by Resurrector 2016-01-27 8:13 PM
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Expert 5K+
Posts: 8948
Location: WHEELING,WV.>>>HOME OF WWVA | those vibrant have a steel inner lip like modern head gaskets , which makes em tough . i've used 1/4 flanges all the time , even if i cut my own . when you weld em up they are going to warp
some again and will need straight edged again --------------------------------------------------later |
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| Ah, sorry Chuck, thought they were like the cheap ones from Napa or wherever...good to know. I've found that too with 1/4" flanges, that's why I'm using 1/2" plate. The ultimate solution would be to get a metal shop to cut some out of heavy plate with a computer controlled cutting machine, problem is they charge a lot unless you order a bunch of them. |
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Veteran
Posts: 131
| Not 1/2" but Accurate carries a 3/8" flange.
http://www.accurateltd.com/Flange-HP-Mopar-2-12_p_213.html |
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Location: North Australia | This is off-topic from the original post but..........
for those contemplating using the copper (head to cast iron manifold) gaskets, be very careful.
I fitted these to my Imperials 413 engine and broke the outside ears off the manifolds. I was on the 3rd one before I realised why it felt odd when tightening up. The gaskets don't compress like you would think.
No gaskets on this engines exhaust manifolds originally. I used a smear of exhaust gasket goo once the manifolds were repaired and no leaks so far, although I did re-tension once after a few hours running. The surfaces on my heads and manifolds were not too bad.
I did use the gaskets to help match up the head and manifold ports, and my 9/16 spanner I was using when I broke the manifolds is still MIA (I threw it out the door).
As to the OP, you could try a high temperature gasket material, graphite with stainless steel re-enforcing, This stuff is used on industrial gas turbines etc. Tricky to cut but tough as nails. You should be able to source at an industrial supplier.
Steve.
Edited by 60 Imp 2016-01-30 7:44 PM
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Board Moderator & Exner Expert 10K+
Posts: 13055
Location: Southern Sweden - Sturkö island | My homemade ones are totally sealed and I never had any issues with them.
http://www.forwardlook.net/forums/forums/thread-view.asp?tid=28754&... flange&highlightmode=1#M203829
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| Steve, that would be a sickening feeling....! Thanks for the warning. Good idea on the industrial stuff, that's pretty much what Remflex is, graphite anyways.
Wizard, I greatly admire your outside the box flange idea, and the superb craftsmanship, how did you bend the exhaust pipe end flat like that? |
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Expert 5K+
Posts: 7434
Location: northern germany |
yes....BUT be careful when you tighten this kind of flange seal. those ex manifolds ears easily break. i always use the the upper end of a cut spray can. its a crush seal 0 ring and works great but just like this it leaves some distance between the flange and manifold ears and when you over tighten it can break. |
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| Good point, 60Fury. I agree, and good idea with the paint can. I ended up modifying a chunk of 2" pipe to fit snugly up in the manifold, and goes down into the pipe a couple inches both ways, like Mopar did apparently until they decided it was too costly (According to Rodger). No seal to fail that way. I believe GM did this in later years, if nothing else it blocks hot exhaust from burning away the seal. I also filed my flanges flat AND used Remflex gaskets, it's a pain in the azz job so I'm bloody well covering all my bases!! Luckily 2" exhaust pipe fits perfectly inside the manifold, and fit with a little filing and tweaking on one exhaust flange, the other was a smaller diameter for some reason so I cut a slit in another chunk of 2", squeezed it together and welded it to the other 2" piece. In hindsight it may have been easier to look for a reducer piece at a parts store, or possibly a muffler shop could make something up for you.
So for anyone with manifolds with flat flanges, please take my advice and do what I did BEFORE you put your engine and exhaust in, it's a simple job then. If you're flanges are warped (if they're used, odds are good they are) any gasket will likely fail.
If I ever do this again, like building a car that needs exhaust from scratch, it would be massively simpler to cut a nice thick flange, and size it and the header pipe so a stock piece of 2" pipe fits perfectly inside it; would save lots of hassle. Another though I had was trying running a hole saw in the manifold, to cut the inside out to be a nice true standard diameter like say 2 1/4"; that would make the transition from manifold to header pipe virtually seamless, with no restriction.
Edited by Resurrector 2016-02-02 10:42 PM
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Member
Posts: 10
| Resurrector - 2016-01-27 5:08 AM
My flanges, when mated together, have a good 1/16" space on either side.
Obviously that needs to be flat. If they were flat, do they sit flat against the manifold. If you were to hold the flanges together, would they touch on one side, and leave a gap on the other side so you have to squeeze everything together with the bolts? Try loosening the pipes further down the line so everything can move around when you line up the flanges, tighten those first, then tighten everything else down the line. Last thing, if either of these are happening, a thick gasket won't help. When you run the bolts or nuts down, you're squishing the thick gasket, and that's bending the flange. See if you can get a thin, embossed steel type gasket to seal. Thick gaskets and overtightening obviously leads to leaks.
Edited by target 2016-02-21 2:42 AM
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Tips for getting exhaust flanges to seal?
